The invention relates to a test agent generation system for producing a constant concentration of test agent vapor or aerosol at controlled condition of temperature and relative humidity for use in calibrating and testing the agent, e.g., the toxic agents HD, GB and VX and other chemical vapors and aerosols, sensitivity of point source alarm systems.
The invention also relates to a vapor and aerosol dilution apparatus which can provide varied and controlled temperature and humidity conditions of agent for testing the performance of detection apparatus under simulated atmospheric conditions of temperature and relative humidity paralleling expected operational environments.
The problem of reliably determining the minimum agent detection capability of various toxic chemical vapor and aerosol detectors, e.g., a point source detection system, under field operational conditions has long existed in the art.
Several prior art methods have been used for determining the toxic agent detection capability of an alarm in the field. Quinine sulfate solutions, for example, have been introduced into the cell of point source agent alarms to check the optical and electrical systems. These solutions do not, however, check the alarm systems capability to sample the atmosphere, extract suspected agent from the air and chemically react the agent with the alarm system.
Various devices containing the actual agent under static conditions, either in solution or in an absorbent material, have been used to provide a test vapor, but have not been proven to be reliable for producing the constant vapor of agent required for use in determining the detection concentration capability of the alarm in the field. The vapor output from these devices is changeable to a degree from changes in air temperature. In addition, the generator vapor, when not in use, is contained under static conditions and consequently, the vapor eluted under dynamic conditions could not be at equilibrium.
A laboratory method of generation, low, constant and reliable concentrations of agent is with a glass vapor dilution apparatus containing agent in a pure form. This apparatus requires at least 24 hours to stabilize after initial servicing with agent and lengthy equilibration times are required for each adjustment of vapor concentration. This apparatus uses a regular house line for compressed air and nitrogen, which generally results in air mixture having a very low relative humidity and consequently only gives a limited, and sometimes false, indication of the performance of the detector being tested.
The portable agent generator described in U.S. Pat. No. 4,069,701 to Frederick C. Baldauf and Kwok Y. Ong, issued Jan. 24, 1978, provides a readily transportable generator which succeeded in providing a low, constant vapor of test agent at rapid equilibration times and with a concentration of agent directly related to air flow rate. This generator, however, is also limited to only the use of existing climatic conditions which vary from day to day, and therefore resulted in varying evaluations of the detector being tested.
Subsequent to the development of the above portable agent generator, applicants were the first to recognize that many detector items, such as the point source agent alarm (i.e., the Army M256 Ionization Dectector Kit), perform differently under different climatic conditions and are particularly sensitive to changes in relative humidity of the operating environment. The phenomenon of relative humidity effects upon the operation of toxic agent vapor and aerosol detectors was not previously appreciated in the art prior to applicants' invention since there was no existing system for rapidly generating a reliable and stable concentration of agent vapor under varying relative humidity conditions.
The present invention was conceived and reduced to practice to provide a complete system which would simultaneously provide a very reliable and stable concentration of chemical agent vapor or aerosol and simulate various relative humidity conditions. The present system can also produce variable temperature control for a range of agent concentration generation and will allow for testing of detectors by means of either static or dynamic exposure to the test agent vapor and aerosol.